The purpose of the studies outlined in this application is to gain a fuller understanding of the metabolism of pulmonary surfactant, with particular reference to the origin of the palmitate in surfactant lecithin. Studies will be carried out to examine the effects of essential fatty acid deficiency upon fatty synthesis and desaturation and on lecithin synthesis and composition in adult rats. Other studies will examine the influence of experimental "diabetes" in pregnant rats on the synthesis of fatty acids and on surfactant lecithin composition in the fetus. 1-14C acetate and 1-14C butyrate will be used as tracers for experiments to measure fatty acid synthesis in lung tissue in these animal models. 1-14C palmitate will be used to examine fatty acid desaturation in these animals and to evaluate the role of plasma free fatty acids as a source of surfactant lecithin fatty acids. Light and electron microscopic studies will be used to correlate changes in these biochemical parameters with alterations in lung structure. Since surfactant lecithin synthesis occurs in type II cells, studies will be performed in pure type II cell cultures to confirm the in vivo data in these specific cells. Studies of surfactant phospholipid composition will be carried out in patients who develop respiratory distress following severe trauma or head injury.